When one of the visiting Gambian teachers cleared his throat and spat out of the car window, I knew we could be in trouble. We were stuck in London traffic and the pavement was crammed with football fans - not known for their patience with cultural differences - on their way to White Hart Lane stadium.
We hastily took a left turn, became lost and walked to the stadium from another part of London. Once inside the ground, it was our visitors' turn to be shaken by differences in culture and custom: more than 30 uninterrupted years of rural West African life until yesterday; now thousands of contorted faces variously singing, swearing and shouting at the top of their voices.
"You don't know what you're doing," one section of the crowd chanted repeatedly at the referee. It might equally have applied to us in our efforts that day to entertain our guests. Things scarcely improved later on. Still exhausted after their flight and shell-shocked after the football, our two visitors were then guests of honour at a dinner party. One of them looked wearily down at the vast plate of Gambian-style food presented to him, rested his forehead on the tablecloth and fell asleep. Equally strangely, the English people at the table continued to converse over his head as if nothing unusual had happened.
Do not misinterpret me. Our long-standing link with a Gambian school is a valuable educational venture. Some students and staff have become wiser as a result of these visits. We have all gained from the connection and students will remember our Gambia-themed initiatives and activities long after they have forgotten everything else about their schooldays.
The football match and the sleeping dinner guest illustrate a wonderful aspect of our Gambian link: the sheer mystery of it all, even after 10 years. One side is never quite sure what to expect from the other. We may find some Gambian behaviour slightly odd and I am certain that the Gambians find us equally eccentric, if not more so.
Imagine the bewilderment on the last trip to Gambia, for instance, when one of my colleagues rushed to apologise to his Gambian hosts for stepping on their cat during an evening stroll. The hosts were mystified - they did not own a cat. An investigation with a torch revealed that our friend had trodden on his own sweater, which had fallen from his bag.
In this increasingly globalised world, the educational worth of such a relationship is immense, notwithstanding the occasional lack of comprehension. Ideally, each school in the modern world should have links with several schools abroad, sharing everything - if only via the internet - from student life stories to teacher lesson plans. However, the same computing technology that has made such a vision possible has also brought to education - internationally - the tyranny of the spreadsheet. Education that you cannot measure numerically has surely never counted for less.
Stephen Petty is head of humanities at Lord Williams's School in Thame, Oxfordshire, England.